Furnaces for the production of silicon metal which employ a tube for feeding the charge into the furnace reaction area are known. For example, furnaces for the production of silicon metal which provide charge feed tubes are described in U.S. Pat. Nos. 4,756,004 (Stanley); 4,756,813 (Stanley et al.); and 4,865,643 (Goins, Jr. and Stanley).
A typical furnace for the production of silicon metal or a silicon metal alloy (e.g., a ferro-silicon alloy) supplies a source of silicon, such as silicon dioxide, to the reaction zone of the furnace. The reaction of a silicon containing material with an oxide also produces silicon monoxide gas which may exit the furnace. When a charge feed tube is used, the silicon monoxide gas can rise through the feed tube.
A problem that has long existed in this type of furnace is that the charge feed tube becomes blocked, which prevents further feeding of charge into the furnace reaction area and requires the furnace to be shut down to remove the blocking material. Of the many prior designs for furnaces with charge feed tubes, none has been successful in avoiding blockage of the feed tube.